1. Field of the Invention
The present invention relates to the battery terminal connecting devices which connect a battery mounted on an automotive vehicle to electrical equipment or accessories mounted on the vehicle which are operated by electric power supplied from the battery, or which provide electric power to the battery. More particularly, the present invention relates to an improvement in and relating to a battery terminal connecting device, which is attached to the end of one or a plurality of leads which connect the battery to vehicle equipment and/or accessories, and which is releasably attached to a battery terminal post.
2. Description of the Prior Art
It is conventional to equip an automotive vehicle with one or more storage batteries, with battery terminal posts, for accumulating electricity and for supplying electric power to various equipment and accessories provided on the vehicle, such as, for example, an electric self starter for the engine, vehicle running lights such as head lamps, a broadcast radio receiver, an alternator which supplies electric power to the battery, and so on. Cables from these various units are provided as brought together into a main cable, and it is well known in the art to provide on the end of this main cable a battery terminal connection device, which is a connector engageable to the battery terminal post.
For mounting and dismounting of the battery to and from the automotive vehicle, and for replacement of the battery, it is convenient for this battery terminal connecting device to be easily releasably attachable and detachable to the battery terminal post. Further, although usually most of the electrical appliances of the vehicle are supplied from one main cable which is attached to the battery terminal connecting device, it is known in the art for an auxiliary terminal to be arranged on the battery terminal connecting device for an auxiliary electrical cable to be attached detachably thereto by a clip. This construction is often provided so that appliances or equipment connected to said cable may be quickly and easily disconnected from the source of electrical power, i.e. the battery, without the necessity for releasing the battery terminal connecting device from the battery terminal post, which may require special tools, and take a lengthy time in an emergency, for example.
In the prior art, there have been provided various different constructions for the battery terminal connecting device, and for the battery terminal post. It has been practiced to provide the battery terminal post as a flattened lug with a hole therein, through which a nut and bolt are engaged so as to attach a lug with a hole therein, this lug serving as the battery terminal connecting device. However, most modern batteries are provided with battery terminal posts which are cylindrical or are frusta of narrow angled cones. Various constructions of battery terminal connecting device for such battery terminal posts have been proposed.
A typical such construction for such a battery terminal connecting device comprises a connecting portion of a generally cylindrical or slightly conical shape, which is wrapped around the battery terminal post, so as nearly completely to surround it, and is made of an elastically deformable and electrically conducting material, with a pair of extensions, extending from the ends of the wrapped around connecting portion, which are each formed with an aperture. A bolt and nut clamping means is passed through these apertures, and thereby, by tightening the bolt and nut means, the size of the wrapped around connecting portion may be reduced, so that it may exert force on the battery terminal post and clamp on it securely. On the other hand, when it is desired to remove the battery terminal connecting device from the battery terminal post, by loosening the bolt and nut means the size of the cylindrical connecting portion of the connector may be increased, so that it becomes loose on the battery terminal post, and may be easily removed therefrom. Further, the main electrical connecting cable is usually attached to the end of one of the extensions remote from the battery terminal connecting post.
In the case of lead acid storage batteries of the usual sort, which include, typically, highly active chemical substances, it is a frequent occurrence that deposits of various corrosive chemicals, such as sulphates, etc., become gradually, over a period of time, deposited on the terminal and around the battery terminal connecting device. Both for reasons of appearance and cleanliness, and because these deposits tend to reduce the quality of the electrical connection between the battery terminal connecting device and the battery terminal post, it is preferable frequently to remove the battery terminal connecting device from the battery terminal post in order to clean both of them. It is also necessary to remove the battery terminal connecting device from the battery terminal post in order to service or to change the battery. On the other hand, because of vibrations caused while the automotive vehicle is running, and other shocks, there is a requirement that the battery terminal connecting device should be securely and tightly clamped onto the battery terminal post during operation of the automotive vehicle, in order to prevent the possibility that the battery terminal connecting device should accidentally be released from its electrical connection from the battery terminal post, thus interrupting the supply of electrical power to the accessories and appliances of the vehicle. Therefore, in the above described prior art, it is necessary to clamp up the bolt and nut means very tightly, and, accordingly, to elastically deform to a considerable extent the portions of the extensions extending out from the cylindrical connecting portion of the battery terminal connecting device to their apertures through which the bolt and nut means passes, so as to exert considerable force on the battery terminal post. Since it is necessary, as above explained, frequently to remove and replace the battery terminal connecting device from the battery terminal post, this repeated elastic deformation of the connecting portion of the battery terminal connecting device and of the extensions may result in permanent plastic deformation thereof, and over a long period of time this plastic deformation proceeds to such an extent that the battery terminal connecting device will no longer grip the battery terminal post properly, even when the bolt and nut means is screwed up very tightly. Thereby, electrical connection between the battery terminal connecting device and the battery terminal post becomes unreliable, and interruption of electric power supply to the accessories and equipment of the vehicle may occur. Thus, the battery terminal connecting device becomes unsuitable for further service.
The difficulty is that, since the internal surface of the cylindrical or part-conical connecting portion of the conventional battery terminal connecting device is smooth, and closely touches the battery terminal post almost all around its circumference, the contacting area therebetween is relatively large, and therefore, in order to provide a given required contact force per unit area between the surface of the contact terminal connecting device and the battery terminal post, sufficient for good electrical contact therebetween, a considerable total force must be provided by the bolt and nut means. This force inevitably causes damage over a long period of service to the battery terminal connecting device. If the contact clamping force per unit contact area between the connecting portion of the connector and the battery terminal post is not sufficient, since the internal surface of the connecting portion is smooth, as is also the battery terminal post, there is a danger that the battery terminal connecting device may easily turn on the battery terminal post. Such turning leads very quickly to electrical disconnection between the battery terminal connecting device and the battery terminal post, and even to physical disconnection, which can lead to an electrical accident, and even fire.
In order to restrict the production of the above described sulphates and chemical deposits on and around the battery terminal post, and also to promote easy removability of the battery terminal connecting device from the battery terminal post, when it is desired so to remove it, it has been commonly practiced to apply a lubricant such as petroleum jelly or other well known lubricants between the battery terminal connecting device and the battery terminal post, when connecting them. However, with the conventional designs of battery terminal connecting device as described above, almost all of such lubricant is inevitably squeezed out from between the battery terminal connecting device and the battery terminal post, as soon as the clamping means, such as a nut and bolt, is tightened up, because their cooperating surfaces are smooth and mate snugly. Such lubricant therefore tends to have little long term effect.
A second type of prior art battery terminal connecting device is one wherein the contacting area between the connecting portion of the battery terminal connecting device and the battery terminal post is not a simple cylinder or frustum of a cone, but is rather two separate cylindrical rings. Each of these rings has extensions, and the two extensions on each side are joined together by a cross piece with a hole bored therethrough, clamping means being passed through these holes, as before. Effectively, this kind of battery terminal connecting device is equivalent to two thin ones of the normal conventional sort of battery terminal connecting device described above, installed one above the other, and the problem still remains that, because, taking each of the rings individually, the cross-sectional area of the part of the ring's extension which transmits force from the clamping means to the part of the ring which contacts the battery terminal post bears a similar relationship as in the above described prior art to the contacting area between the ring and the battery terminal post, there still remains the problem of deformation of this part of the extensions, if sufficient pressure is to be brought to bear between the battery terminal connecting device and the battery terminal post, per square unit of contact area, to establish good electrical contact therebetween.